Thread clamping device including internal sensing, reporting and external detector

ABSTRACT

The present device relates to a thread clamping device including a plurality of movable segments with threaded inner surfaces suitable for engaging a threaded rod and including a strain gauge and transmitter therein for measuring the actual strain on the device and for transmitting this information to a receiver external to the thread clamping device, such as a receiver and display integral with a wrench for applying torque to the thread clamping device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of our co-pendingapplication Ser. No. 13/385,178 filed Feb. 6, 2012 which claims priorityfrom provisional patent application Ser. No. 61/462,707 filed Feb. 7,2011. The present application claims priority from all the foregoing,and the entire contents the foregoing are incorporated herein byreference for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

(none)

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates generally to the field of threaded fasteners orthread clamping devices, and more particularly to a thread clampingdevice capable of internally measuring the tension load on the deviceand capable of remotely reporting the measured load and a uniqueidentification code electronically, typically employing RFID (RadioFrequency Identification) technology.

2. Description of the Prior Art

The fastener industry has several examples of threaded female fastenerswith moving segments that facilitate quick connection or assembly of thefastener to a threaded rod when assembled in one direction (moved alongthe threaded rod), but locks when linear motion (without rotation) ofthe fastener along the threaded rod is attempted in the oppositedirection. That is, the fastener can be moved along a threaded rod inone direction rapidly and without rotation (hereinafter the “ratcheting”direction), but locks when motion is attempted along the rod in theopposite direction (hereinafter the “locking” direction), requiringrotation of the fastener to move the fastener in the locking direction.Upon applying an external torque to tighten the fastener, the fastenerwill drive its segments tightly against the threaded rod (if thefastener base can rotate), but not move axially along the rod, thusproviding locking friction between the segment threads and the rodthreads.

However, existing fasteners generally lack the capability to measure theactual load on the fastener and then communicate the measured load valueto a remote receiving station. (Note: It is normal procedure tocommunicate to the remote receiving station an identifier that specifieswhich fastener generated the transmitted data along with such data. Thisis to be understood in the following descriptions even though anexplicit recitation of transmitted identifier may not be provided in allcases.) When received by a remote receiving station, such informationwould be useful for several purposes including ascertaining if thefastener is bearing the proper load, not so large as to threaten failurenor so small as to imply improper installation or some other defect inthe utilization of the fasteners.

It is common for fasteners to be installed with a torque wrench capableof applying a known and specified amount of torque to the fastenerduring installation, but this does not directly determine the actualload on the fastener during service. In particular, information aboutchanges in the actual load experienced by the fastener during itsservice life, whether arising from wear on this or another componentpart or another cause, is unknown. Thus, a need exists in the art fordevices and procedures for the in-service determination andcommunication of the load being born by a thread clamping device inservice on a threaded rod.

SUMMARY OF THE INVENTION

Accordingly and advantageously the present invention relates to a threadclamping device including a plurality of movable segments with threadedinner surfaces suitable for engaging a threaded rod and including astrain gauge therein for measuring the actual strain on the device.

In addition to measuring the actual strain experienced by the threadclamping device, some embodiments of the present invention also relateto a transmitter for transmitting to a remote receiving station theactual strain measured, typically including a suitable identificationcode for determining which device is transmitting.

These and other features and advantages of the present invention will beunderstood upon consideration of the following detailed description ofthe invention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. The drawings herein are schematic, not to scale and therelative dimensions of various elements in the drawings are not toscale.

Some of the drawings depict threaded structures having internal threads,external threads or both. An artifact in the drawing program producesthreads whose depiction in the figures may appear as lacking the truespiral structure of actual threads, although the thread profile isproperly depicted. However, the threads are depicted herein for purposesof explaining various structures, embodiments and/or other features oruses in connection with the present invention, and the possible apparentabsence of spirals in the depiction does not affect the variousdescriptions presented.

The techniques of the present invention can readily be understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 is a perspective view of a typical E-TCD engaged with a threadedrod.

FIG. 2 is a top view of a typical E-TCD.

FIG. 3 is a side view of a typical E-TCD.

FIG. 4 is an exploded perspective view of a typical E-TCD.

FIG. 5 is a perspective view of a typical E-TCD with the cap removed

FIG. 6 is a top view of the base.

FIG. 7 is a cross section of the base taken along 7-7 of FIG. 6.

FIG. 8 is a perspective, sectioned view of the cap, strain ring andbase.

FIG. 9 is a cross section of rod, cap, segments and base taken along 9-9of FIG. 2 with the addition of a threaded rod not shown in FIG. 2.

FIG. 10 is a perspective view of a typical segment.

FIG. 11 is a block diagram of typical basic electrical functionsincluding printed circuit board and strain gauge (strain sensor)circuitry.

DETAILED DESCRIPTION

After considering the following description, those skilled in the artwill clearly realize that the teachings of the invention can be readilyutilized in the determination and communication of loads born by athread clamping device in service as attached to a threaded rod.

Prior approaches to the problem of ascertaining the actual load on afastener while in use have typically used the measurement of torque onthe fastener to infer the tension load on the fastener, and therebyprovide information that the fastener is or is not within desired loadlimits for the particular nut/bolt connection. A common tool used totighten a nut or bolt to a certain torque is referred to as a “torque”wrench. A conventional torque wrench provides information on the torqueapplied to the fastener, but does not directly provide information as tothe load on the fastener achieved by the application of any particulartorque. It is envisioned in some embodiments of the present inventionthat the thread clamping devices with electronic sensing pursuant tosome embodiments of the present invention(“E-TCD”) would make use of aspecially modified torque-type wrench, a “load wrench,” to perform thetask of tightening fasteners but, rather than merely providinginformation about the applied torque, the load wrench, would includespecially constructed on-board sensing and communication capabilities tocommunicate with sensors in the E-TCD and thus receive information onthe actual fastener load. Such a load wrench is advantageouslyenvisioned to be a typical tightening tool modified to communicate withthe E-TCD , typically by means of the appropriate RFID protocol. Thatis, the load wrench would be one example of the “remote receivingstation” with which the E-TCD communicates, although one or moreadditional remote receiving stations will typically be employed as wellin connection with some embodiments of the present invention. Thus, theload wrench would typically have a visual display showing the actualload on the E-TCD, as communicated directly to the load wrench from theE-TCD as it is being tightened or loosened, allowing the user of theload wrench to observe the actual load on the fastener. Although sensingand communication capabilities as described herein can be employed inconnection with many types of fasteners, it is envisioned that thefastener described in EP 1819930 and US 2007/0286702 A1 will beadvantageous for this purpose. The E-TCDs pursuant to some embodimentsof the present invention include the capability to measure directly thetension load on the fastener or the connecting threaded rod (the loadsare the same) by measuring the deflection (or strain) internal to theE-TCD. This deflection or strain is directly proportional to the E-TCDtension load. Upon command this measured strain is translated into adigital word which may be transmitted to a remote receiving station suchas an RFID reader after the RFID reader sends an interrogating signal tothe E-TCD. It is envisioned that the tension load data and a codeidentifying the particular fastener can be supplied using conventionalRFID technology, defined as a Class 2 RFID Tag operating with theappropriate RFID reader (interrogator), thereby providing mechanicaldata not otherwise available to the user through conventional RFIDdevices.

The E-TCD devices pursuant to some embodiments of the present inventionthus provide the capability to communicate the E-TCD tension load andthe E-TCD unique identification code remotely to the RFIDreader-interrogator, and through other typical communication means (suchas an Internet connection) to virtually any other location.

In brief, the E-TCDs described herein engage the threads on a threadedrod (or simply “rod”) by means of a number of threaded, movable segmentswherein the threads of each segment are capable of robust engagementwith the threads of a rod, typically different segments or groups ofsegments capable of binding with different thread structures.

The structure of threads on threaded rods may be defined according toprofile geometry, diametral pitch, axial pitch and dimension among othercharacteristics. See for example, Machinery's Handbook, 28^(th) Ed.(Industrial Press, 2008), pp. 1708-2026. The diameter of the rod alsoaffects the geometry of the threads thereon. For economy of language, weuse “thread type”, “thread structure”, “thread geometry” and the like todenote a particular thread configuration on a rod with a particulardiameter.

The movable segments of the E-TCD may (but need not) have differentthread structures capable of engaging corresponding thread structures ondifferent types of rods. That is, each movable segment (or set ofsegments) of an E-TCD can be designed to meet the standards for aparticular thread on a particular rod, allowing thereby a single E-TCDdevice to be suitable for use with more than one type of rod byincluding segments having different thread structures within a singleE-TCD device. However, to be concrete in our discussions, we describethe case in which all segments have the same structure, not intendingthereby to exclude E-TCDs containing different types of segments. SuchE-TCD's with a single segment type are expected to be important inpractice since the expense of manufacturing multiple segment types isavoided and the complications of assembling different segments types inthe proper arrangement within a single E-TCD is likewise avoided.

In view of the foregoing, in accordance with the various embodiments ofthe present invention, there is provided a family of E-TCDs able to movealong a threaded rod in one direction without rotation (“ratchetingdirection” or “downward”), and further, will not move in the oppositedirection without rotation (“locking direction” or “upward”). Each timethe E-TCD moves (slides) at least a one half (½) thread downward (in theratcheting direction) the E-TCD is configured to internally ratchet andlock in place, thus preventing the E-TCD from moving upward (in thelocking direction) with respect to the threaded rod.

Additionally, an advantage of the E-TCD described herein over atraditional hex nut is that the E-TCD will typically be capable ofsuccessfully engaging threaded rods having damaged threads where even asubstantial portion of the threads of the rod have been deformed to thepoint where the standard hex nut will jam. These and other features andadvantages of the present invention will be understood uponconsideration of the following detailed description of the invention andthe accompanying drawings.

To be concrete in our discussion, we describe in detail the embodimenthaving four identical segments collecting data via a strain gauge andcommunicating with remote device(s) by means of RFID technology.Different numbers of segments, different types of segments and/or othermodifications will be apparent to one having ordinary skill in the art,and are included within the scope of the present invention.

FIG. 1 is a perspective view of a typical E-TCD 2 engaged with athreaded rod 4 in accordance with some embodiments of the presentinvention. FIG. 2 and FIG. 3 show top view, and side view respectivelyof a typical E-TCD, 2.

FIG. 2 illustrates for this particular embodiment four segments 6,symmetrically positioned about the central axis of the E-TCD, 2. Alsoshown are hex surfaces 21. While the base 22 is shown with substantiallyhexagonal side surfaces, base 22 of the E-TCD 2 can also includes cubic,square and any other tubular configuration capable of accommodatingthreaded rod 4, and which is capable of including the components andfeatures of the E-TCD 2, within the scope of the present invention.

FIG. 4 illustrates a complete E-TCD 2 with all parts exploded. All theparts illustrated in FIG. 4, when assembled, comprise a complete E-TCD 2as would be employed for actual field uses. Shown in FIG. 4 are loadbearing surfaces 18 in base 22 that engage and support outer surface 16of segments 6. There are, in this example, four load bearing surfaces 18arranged in an equidistant polar array relative to central axis 24 (seeFIG. 7) in base 22 (see FIG. 6). The E-TCD 2 has its central axis 24coincident with the axis of threaded rod 4. Left guide surface 17, loadbearing surface 18 and right guide surface 19 are defined as a featureset. Also load bearing surface 18 is advantageously designed to beinclined approximately 30 degrees relative to central axis 24.

FIG. 4 also shows a spring groove 14. There is one spring groove 14, oneupper guide surface 12 and one outer surface 16 for each segment 6. Inthis example, we show four posts 20 on base 22. The four posts 20 onbase 22 are used to couple cap 8 and strain ring 25 to base 22. Alsoshown are antenna 15 and printed circuit board 23 sliced in half suchthat strain gauge 27 and connecting wires 29 are readily visible. Withinthe scope of the present invention, depending upon the shape of E-TCD 2and the number of segments, more or fewer posts 20 may be used. Abovebase 22 is shown spring 10. In a fully assembled E-TCD 2 the antenna 15and printed circuit board 23 typically reside in the cap 8. Strain gauge27 is securely bonded to the inside surface 33 of strain ring 25. Wires29 carry the strain gauge information to printed circuit board 23. Thecircuitry on printed circuit board 23 processes the information from thestrain gauge and transmits the gauge information and a uniqueidentification code via an RF signal from antenna 15, typically uponreceipt of a transmit request, likewise received through antenna 15.

FIG. 5 is a perspective view of a typical E-TCD 2 with cap 8 removedexposing segments 6, spring 10, antenna 15, printed circuit board 23,wires 29, strain ring 25 and barbs 31. Also shown is base 22.

FIG. 6 is a top view of base 22. Shown in top view are left guidesurfaces 17, load bearing surfaces 18, right guide surfaces 19 and base22. Also, press fit surfaces 28 on posts 20 and outer hex surfaces 21are shown.

FIG. 7 shows load bearing surfaces 18 at a 30 degree angle to centralaxis 24. Now referring back to FIG. 4, in an assembled configuration,outer surfaces 16 bear against load bearing surfaces 18 of base 22.During application of clockwise torque upon hex surfaces 21 of base 22left guide surfaces 17 engage right side surfaces 11 of segments 6 andcause segments 6 to rotate clockwise (when viewed from above in thesense of FIG. 4) about threaded rod 4. Similarly, during application ofcounter-clockwise torque upon hex surfaces 21 of base 22, right guidesurfaces 19 of base 22 engage left side surfaces 13 of segments 6 andcause segments 6 to rotate counter-clockwise about threaded rod 4. Itshould be noted that E-TCD 2 will operate correctly even if left guidesurfaces 17 of base 22 and right guide surfaces 19 of base 22 do notengage right side surfaces 11 of segments 6, and left side surfaces 13of segment 6 respectively, provided that load bearing surfaces 18 ofbase 22 are engaged with outer surfaces 16 of segments 6. It should alsobe noted that segments 6 engage the rod threads (as shown in FIG. 9).

FIG. 8 shows base 22, strain ring 25 and cap 8 sliced in half. This viewspecifically illustrates how cap 8 is attached in this example to base22 using the barbs 31 on strain ring 25. During assembly of the E-TCD,strain ring 25 is press fit over base press fit surfaces 28. Thisoperation expands the strain ring 25 and provides for a secureattachment of the strain ring to the base. Now to attach the cap 8(advantageously made of plastic) it is pressed over strain ring barbs 31that engage cap inner surface 35. If the cap 8 is attempted to beremoved the barbs 31 dig into the inner surface 35 and provide a highretention force preventing cap removal.

FIG. 9 is a cross sectional view of E-TCD 2 as defined by Section 9-9shown in FIG. 2 with segments 6 engaged with threaded rod 4 inaccordance with some embodiments of the present invention. Also shown incross section is cap 8, and base 22 along with spring 10. Also shown aremotion direction arrow right 50 and motion direction arrow left 52 thatdefine the direction of motion of segments 6 during ratcheting.

FIG. 10 is a perspective view of a typical movable segment 6. Thethreads of segment 6, 40, are chosen in this example to match the threadgeometry of threaded rod 4 and therefore engage the threads of threadedrod 4. While the thread phase could be different among segments withinan E-TCD 2 it is more economical if all the segments are identical.

FIG. 11 is an electrical block diagram graphically describing typicalcircuitry for handling electrical signal from the strain gauge to theA/D (analog to digital) converter to the RFID IC (integrated circuit)and then transmitted via the antenna to the reader where the signal isreceived and interpreted as the unique identifying code and strain valuefor the specific E-TCD 2.

Typical E-TCDs described herein are capable of two fundamentalfunctions. One is the mechanical function and the other is theelectrical function. To understand the mechanical function we refer toFIG. 1 and describe a typical example of mechanical function. Thisexemplary E-TCD 2 is typically configured to move along threaded rod 4in one direction (“ratcheting direction”) without rotation of E-TCD 2,and to not move in the opposite direction (“locking direction”) withoutrotation. (For the purposes of describing E-TCD 2 and relatedembodiments, the direction of motion whereby E-TCD 2 moves alongthreaded rod 4 without rotation shall be defined as the ratchetingdirection and the opposite direction of motion as the non-ratcheting orlocking direction.) In particular, in accordance with some embodimentsof the present invention, E-TCD 2 is typically configured to be engagedto threaded rod 4 such that a single downward hand movement of E-TCD 2down the length of threaded rod 4 will correspondingly move E-TCD 2 inthe ratcheting direction, generally to a predetermined position onthreaded rod 4. Once in place, an upward hand movement of E-TCD 2 alongthe length of threaded rod 4 will be met with an equal and oppositeforce such that E-TCD 2 will not move in the non-ratcheting direction.Rather, in order to move E-TCD 2 in the upward non-ratcheting directionof threaded rod 4, E-TCD 2 is rotated along the threads of threaded rod4. The most common configuration with respect to E-TCD 2 engaged to avertical threaded rod 4 is where (when viewed from above) acounter-clockwise rotation of E-TCD 2 will advance E-TCD 2 upward(non-ratcheting direction) with respect to threaded rod 4.

It should be noted that while the above description is provided withrespect to upward (non-ratcheting) and downward (ratcheting) handmovements of E-TCD 2 along the length of threaded rod 4, the directionof the movements of E-TCD 2 may be arbitrary depending upon, forexample, the position of threaded rod 4 to which E-TCD 2 is engaged.

In some embodiments, E-TCD 2 will ratchet whenever E-TCD 2 is movedalong threaded rod 4 a minimum of one half (½) of a thread pitch in theratcheting direction. That is, when E-TCD 2 moves one half of a threadpitch the segment set that matches the rod thread will ratchet such thatif forces try to move the segment set in the opposite non-ratchetingdirection, a minimum of one segment will lock up and prevent motion inthe opposite direction with respect to threaded rod 4. To implement ½thread ratcheting 2 identical segments 6 are arranged opposite oneanother in two of the possible positions (shown in FIG. 7).

In particular, with respect to FIG. 7 and FIG. 9, each of the twosegments are driven upwards and outward at a 30 degree angle relative tocentral axis 24 as a result of upper guide surface 12 (FIG. 9 showsguide surface 30 engaging bearing upper guide surface 12) engaging capguide surface 30 as threaded rod 4 (or equivalently the E-TCD 2) ispushed in the ratcheting direction. In this case, with sufficientmovement of the segments along motion direction arrow right 50 andmotion direction arrow left 52 (FIG. 9) segments 6 will completelydisengage from the threads of threaded rod 4, and re-engage when thenext rod thread moves into position to allow the two segments 6 to movetoward the central axis of threaded rod 4 and re-engage the threads ofthreaded rod 4.

On the other hand, if the forces reverse in direction and threaded rod 4is driven down in the non-ratcheting direction (or E-TCD 2 is drivenup), segments will be driven toward threaded rod 4 and lock. The threadswill stay engaged as long as the downward force exists because of theinward radial force pushing segments 6 toward threaded rod 4. The inwardradial force is generated by (see FIGS. 4, 5 and 6) load bearingsurfaces 18 of base 22 contacting outer surfaces 16 of segments 6. Alsoto be considered is the outward radial force caused by the interactionof thread flanks of threaded rod 4 against top thread flank 42 ofsegment 6 (FIG. 11). The inward radial force relative to axis 24 onsegment 6 overcomes the outward radial force on segment 6 as long as the“flank angle”, the included angle between top thread flank 42 of segment6 and the bottom thread flank 44 (FIG. 10) remains approximately 60degrees which is the standard flank angle for American Standard andMetric threads, and the angle of load bearing surface 18, remainssubstantially 30 degrees relative to axis 24, and the reversing forces(forces in the non-ratcheting direction) are present. The resultantinward force keeps the segments 6 engaged with threaded rod 4.

Moreover, in some embodiments of the present invention, the materialused to construct segments 6 is chosen to have a yield point greaterthan or equal to that of the material used for fabrication of threadedrod 4. Even when the yield points are substantially similar between thematerials for threaded rod 4 and segments 6, and one segment 6 beginsplastic deformation, as soon as threaded rod 4 moves (that is, beforeall segments of the segment set are fully engaged and resisting themotion of the threaded rod), other segments 6 will start to engagethreaded rod 4 to overcome the strength of threaded rod 4. Actualexperiments have shown that upon application of an increasing load onthreaded rod 4 while engaged with segments 6, segments 6 will crush thethreaded rod 4 and the threaded rod 4 will fail by separating in two,typically at a point just below the segments 6. That is, if the systemis placed under increasing axial force in the non-ratcheting direction)between the rod and the E-TCD 2 until failure occurs, the rod ratherthan the E-TCD 2 is the element most likely to fail. The segments 6 aretypically much stronger and transfer more load per thread 40 to thethreaded rod 4 than a standard hex nut with the same number of threadsand of the same thread geometry because the E-TCD 2 provides inwardradial forces that place the segment 6 threads 40 material incompression and not just in shear as is the case with a standard hex nuthaving thread elements incapable of moving radially toward the threadedrod.

Alternatively, the material for segments 6, may have a yield pointsubstantially lower than that for threaded rod 4, in which case threadedrod 4 will still fail (i.e., give way or break off) before E-TCD 2 iscompromised if there is sufficient length of thread engagement.

Moreover, spring 10 in some embodiments is configured to have sufficienttension to cause segments 6 to close around threaded rod 4 even in thecase where there is gravitational force pulling segments 6 away fromthreaded rod 4 (for example, in the case where E-TCD 2 is inverted).Indeed, if segments 6 are not driven toward the central axis of threadedrod 4 by spring force, segments 6, may move outward to the wall of cap 8wall and remain in that position resulting in E-TCD 2 not engaging withthreaded rod 4.

Referring to FIG. 9, the motion direction arrow right 50 and motiondirection arrow left 52 illustrate the line of action in which segments6 are configured to move when E-TCD 2 moves in the ratcheting directionwith respect to threaded rod 4.

During final assembly of these embodiments, the strain ring 25 is pusheddown over posts 20 to be press fit against press fit surface 28 of base22 (FIG. 8). Once the strain ring is in place, cap 8 is aligned over thestrain ring 25 and during assembly the cap inner surface 35 engagesbarbs 31 on strain ring 25 as the cap is pushed down over the strainring. The cap 8 now cannot be removed from the base 22 without damage tothe cap 8. This accomplishes the final assembly of the E-TCD 2 withoutthe use of fasteners.

While the absence of fasteners in the assembly of E-TCD is likely to beadvantageous in practice, some embodiments of the present invention mayemploy fasteners as would be apparent to those having ordinary skill inthe art.

Referring to FIG. 7, a conical lead-in 26 is conveniently used to guidethe E-TCD 2 over the end of threaded rod 4 upon initial engagement ofE-TCD 2 to the end of threaded rod 4. The lead-in 26 causes installationof E-TCD 2 over the end of threaded rod 4 to be quick and easy as thelead-in 26 guides the end of threaded rod 4 to the center of E-TCD 2.The segments 6 then move according to FIG. 9 as previously described assegments 6 engage the end of threaded rod 4.

To measure the tension load on the E-TCD 2 (equivalent to the tensionload in the threaded rod 4 to which the E-TCD 2 is engaged), it isrequired to measure some mechanical parameter that is proportional toload. Unlike many thread fasteners, this is feasible to do in an E-TCD 2as generally described herein because of its advantageous construction.The E-TCD 2 uses moving segments 6 to engage the threads of threaded rod4. The process of thread engagement previously described causes thesegments to be forcibly driven radially into the rod. Now referring toFIG. 4, there also exists a force equal and opposite to this radialforce that is exerted outwardly against the base 22, load bearingsurfaces 18 by outer surfaces 16. The forces against load bearingsurfaces 18 cause the base to expand radially outward. In turn, thiscauses strain ring 25 to expand since the strain ring 25 inside surface33 wraps around base 22 posts 20 and is fitted against press fit surface28.

Again referring to FIG. 4 strain gauge 27 is bonded to inside surface 33and as inside surface 33 expands or contracts so does the gauge 27 thatis bonded to inside surface 33. The expansion and contraction of strainring 25 is proportional to the axial load on threaded rod 4. The straingauge 27 is intimately bonded to strain ring 25 and therefore alsoexpands and contracts in proportion to the axial load on threaded rod 4.

The strain gauge electrical signal is passed to printed circuit board 23via wires 29. The gauge signal is processed by the electrical circuit(FIG. 12) on printed circuit board 23. When commanded by an externalelectrical RF signal received by antenna 15 the electrical circuit onprinted circuit board 23 generates and transmits a signal via antenna15. The electrical power to run the printed circuit board circuitry maybe derived from the original incoming signal or may be provided by alocal power source such as a battery.

In a typical embodiment of the invention, the electrical signals aretaken to comply with standardized RFID protocols. The returned signalfrom printed circuit board 23 contains a unique code identifying thespecific E-TCD 2, and also embedded in the return signal is the value ofstrain provided by the strain gauge 27. Signals from the strain gauge 27do not have to be proportional to the load on threaded rod 4 they onlyhave to be repeatable. In other words the same load on threaded rod 4should produce the same electrical value from gauge 27. Each E-TCD 2 iscalibrated at the factory. The results of the factory calibration arecompiled in a “look up table” and then stored in computer memory and the“look up table” is associated in the computer with the uniqueidentification code of the E-TCD 2. This memory may physically reside onprinted circuit board 23 or reside in any data memory location that isaccessible by the computer processor associated with the RFID readerthat is interrogating the E-TCD 2. The look up table provides an actualtensile load value for any electrical value provided by gauge 27 of thespecific E-TCD 2.

Printed circuit board 23 and antenna 15 are referred to as an RFID tagif the RF protocols being used are consistent with the RFID protocoldefined by ISO standards. The E-TCD 2 embodiment shown in FIG. 4represents a class 2 passive or class 3 semi passive RFID tag althoughthe power source defined in a class 3 tag such as a battery is not shownin FIG. 4. Passive class 2 tags require no power, but have a muchshorter read range than the class 3 semi passive tags that have a powersource allowing higher power transmissions and thus longer transmissiondistances between the E-TCD 2 and the reader (interrogator).

Another advantage and capability of the E-TCD 2 is that a standard RFIDreader (interrogator) may be combined with current cell phonetechnology. This combination is defined as a Cell-Monitoring Station(CMS) which will allow the user to command a computer to communicatewith a specific group of remote E-TCD 2's and request the currenttensile load of each E-TCD 2 within antenna range of the CMS. The CMSmay be commanded to report the current or past tensile load andidentification code of each of the E-TCD 2's within the group. Otheradvantages include the ability of the CMS to be programmed to call aspecific computer and report any condition to which the CMS isprogrammed to respond. This provides to the user the ability to monitorthe security of any device within the CMS network to be sure it issecured or fastened as intended and any abnormalities within thefastening system of E-TCD 2's will be reported.

What is claimed is:
 1. A load wrench for tightening a thread clampingdevice wherein said load wrench is equipped with a receiver for sensingloads transmitted from said thread clamping device, and wherein saidthread clamping device is equipped with a compatible load sensingtransmitter.